1. Field of the Invention
The present invention relates to an imaging apparatus, and more particularly, to an optical image photographing apparatus that is used for ophthalmological diagnosis and treatment or the like.
2. Description of the Related Art
A scanning laser ophthalmoscope (SLO) which uses a principle of a confocal laser microscope is an ophthalmological apparatus that performs a raster scanning on a fundus of the eye with laser light which is measurement light and obtains a planar image of the fundus of the eye based on the intensity of return light with a high resolution at a high speed.
Such an apparatus for photographing a planar image is hereinafter referred to as SLO apparatus.
In recent years, it has become possible to acquire a planar image of a retina with improved lateral resolution by increasing a beam diameter of measuring light in the SLO apparatus. However, along with the increase in the beam diameter of measuring light, there occurs a problem of decreases in an SN ratio and the resolution of a planar image of a retina due to aberration of an eye to be inspected when the planar image is acquired.
In order to solve the problem, there is developed an adaptive optics SLO apparatus including an adaptive optics system, in which aberration of an eye to be inspected is measured by a wavefront sensor in real time, and aberrations of measuring light and return light thereof generated in the eye to be inspected are corrected by a wavefront correction device. Thus, it is possible to acquire a planar image with high lateral resolution.
When a planar image with high lateral resolution is acquired, because of problems of optical aberrations of the apparatus itself and a longer photographing time, a photographing range of a single photography becomes small. As a result, there is a tendency that it becomes difficult to distinguish which part of the fundus the planar image corresponds to. In the invention disclosed in Japanese Patent Application Laid-Open No. 2010-259543, there is proposed a complex apparatus in which an SLO apparatus having a large field angle and an SLO apparatus having a small field angle with high resolution are combined so as to solve the problem.
In order to photograph a desired position of the eye to be inspected, a fixation target for fixating the eye to be inspected is often used. In the invention disclosed in Japanese Patent Application Laid-Open No. 2007-275374, a desired position in the fundus image is specified so as to change a projected position of the fixation target, and hence a fundus image of the desired position is easily acquired.
Here, if the eye to be inspected has ametropia, such as near sightedness or far sightedness, it is necessary to perform focus adjustment so that the subject can clearly see a display of the fixation target or that the acquired planar image can be clearly displayed. In this case, in some configurations of the optical system, a relationship between a display position of the fixation target and an amount of urging the eye to be inspected to rotate depends on a diopter scale of the eye to be inspected. Therefore, it is difficult to acquire a planar image of a desired position of the fundus.